The sales pitches start just a few steps after you cross the border into Mexico. They come in the same half-whispers familiar to tourists who have been offered time-shares and T-shirts. "Excuse me, sir," a Mexican man politely asks in accented English. "Are you looking for a good dentist?"

It wasn't supposed to end this way.
For baby boomers trickling toward retirement, these were going to be the golden years. The good life earned after toiling in some version of the 20th century vineyards.
A big percent of boomers envisioned no work at...